Lamp upgrade makes you a hot-head

[Cameron] decided to give his twenty-year-old headlamp a makeover. He uses it when he’s out for a run and wanted to have more light to see where he’s going, as well as a red tail light on the back. The stock design uses an incandescent bulb on the front of the head band, and a battery pack on the back. He managed to convert the device to output 700 lumens without major changes to the form factor of the unit.

The first change he decided on is to use a Cree XLamp which provides the 700 lumens of light by drawing about 9.5 Watts of power. Obviously the original battery pack isn’t going to do well under that kind of load, so he also sourced a 5000 mAh Lithium battery. A bit of circuit design and PCB layout gives him two driver chips for the four-element LED module, a charging circuit for the battery, and an ATtiny13 to drive the head lamp and flash the red LED tail light. See the blinky goodness in the video after the break.

That’s a lot of light, but we wonder if he experiences a warm forehead from the heat sink used to keep that LED package cool?

That thing is -not- adequately cooled through tiny copper vias inside a closed plastic box. It should be mounted directly on the surface of an anodized heatsink, and the heatsink should be exposed, not covered.

With that setup, I’m guessing the light output should start dropping dramatically in just tens or hundreds of hours.

Yup, heat ~ the LED killer. He does have a heatsink on the back of the LED PCB. It looks like the kind to go on an IC. Hard to see how big this heatsink is. His real power output might also be lower if he’s dimming the LED through PWM.

I’ve played with some 10W LedEngin parts and I had to have some pretty big heatsinks to keep them running at a reasonable temperature.

At least it will be cooler outside at night when he is using it. Especially in the winter.

But as the guy running towards you sometimes only wearing a reflective vest myself, I really hate your bright lights. It completely messes me up. I have to slow down dramatically to get my night vision back without running off the trail.

>> mental picture <<
The kid at the beginning of Despicable Me at the pyramids. When he is sailing through the air with his little jet, except instead of a jet he has this light. And instead of a kid, some old dude.

It wasn’t an oversight. It is conventional to quote batteries of this size in mAh, not Ah (see http://www.all-battery.com/lithiumpolyerbatteries.aspx where all batteries are reported in mAh). Sort of like how a 10,000pF capacitor is not described as 10nF. Furthermore, I am a college professor and I would never deduct marks for something inconsequential like that.